1. Field of the Invention
The present invention relates to a deflection yoke device and particularly to a deflection yoke device provided with a ringing preventing means.
2. Description of the Related Arts
A deflection yoke device is a device for deflecting an electron beam traveling in a CRT. This device has a horizontal deflection coil for deflecting an electron beam in a horizontal direction of the screen and a vertical deflection coil for deflecting it in a vertical direction thereof.
Horizontally and vertically deflecting currents having predetermined frequencies and sawtooth waveforms are respectively supplied to the horizontal deflection coil and the vertical deflection coil. Upon receiving the horizontally and vertically deflecting currents, the horizontal deflection coil and the vertical deflection coil respectively produces horizontally and vertically deflecting magnetic fields. The electron beam is deflected horizontally or vertically by the horizontally and vertically deflecting magnetic fields.
Here, an oscillating component is included in the horizontally deflecting current. The oscillating component is produced at the time of a rise of a sawtooth wave. This phenomenon is called ringing.
The ringing component resulting from the oscillation produces a striped pattern of relative density on the CRT screen (FIG. 5) and a waviness of scanning lines (FIG. 6).
Specifically, the ringing caused by oscillation produces a striped pattern of relative density in the vertical direction of the screen, as shown in FIG. 5. The ringing component (parasitic oscillating component) produces a vertical waviness on the scanning lines, as shown in FIG. 6.
Hitherto, to eliminate such trouble, the vertical deflection coil has been provided with a damping circuit.
FIG. 7 illustrates a circuit configuration of a vertical deflection coil provided with the damping circuit.
In FIG. 7, two vertical deflection coils 10-1 and 10-2 are connected in series. A damping circuit 14.1 formed by connecting a resistor 16-1 and a capacitor 18-1 in series is connected between a high voltage-side terminal 12 disposed at one end of the vertical deflection coil 10-1 and a central point of the vertical deflection coil 10-1. Similarly, a damping circuit 14-2 formed by connecting a resistor 16-2 and a capacitor 18-2 in series is connected between a low voltage-side terminal 20 disposed at one end of the vertical deflection coil 10-2 and a central point of the vertical deflection coil 10-2.
In this configuration, the parasitic oscillating component is substantially eliminated. More specifically, the parasitic oscillating component is attenuated by the resistors 16-1 and 16-2, and a DC component is eliminated by the capacitors 18-1 and 18-2, thereby suppressing the generation of heat in the resistors 16-1 and 16-2.
Conventionally, the vertical deflection coils have generally been fabricated into the form of a so called toroidal winding. In conjunction with the trends in recent years toward larger-size cathode ray tubes and higher definition of the picture, a frequency which is higher than the conventional level has come to be used as a horizontal deflection frequency. If a horizontal deflection is effected at a high frequency, the aforementioned ringing is more likely to occur.
To reduce the effect of ringing as a measure against this situation, it suffices if the vertical deflection coil is wound into the configuration such as is shown in FIG. 8. The winding of this configuration is generally referred to as a saddle-type winding, and has been conventionally employed for the horizontal deflection coil.
The adoption of this configuration makes it slightly difficult for the disturbance of the picture due to ringing to occur.
However, since the horizontal deflection takes place at a high frequency, the effect of ringing on the horizontal deflection coil cannot be eliminated even if a saddle-type vertical deflection coil is used.